This invention relates generally to flooring tools, and in particular to carpet seaming irons.
A carpet seaming iron is a tool commonly used in the installation of carpet in residential settings. The carpet is delivered to the home as a roll good of fixed width. A carpet installer cuts lengths of the carpet off the roll and fits them to the various rooms. As the carpet off the roll is often not as wide as the width of some rooms, seams between two pieces are often necessary. An electric carpet seaming iron is used in conjunction with carpet seaming tape to create such seams. The carpet seaming tape is placed beneath two pieces of carpet to be seamed and centered beneath the seam area. The carpet seaming iron is placed on the tape to melt the thermoplastic adhesive on the face of the carpet seaming tape. Once the thermoplastic adhesive is melted, the iron is moved forward, and the carpet backing is pressed into the molten area of thermoplastic adhesive behind the iron. Once the thermoplastic adhesive cools, the tape forms a permanent patch on the carpet's backing that effectively joins together the adjacent pieces of carpet.
In the design of a carpet seaming iron, for ease of use, it is preferred that the iron's base containing the heating element and temperature controls have as thin a profile as possible. As the iron is moved between the carpet edges in the area to be seamed, a shorter overall thickness (or height) of base creates less disturbance of the carpet that is being seamed. Furthermore, it is preferred to form ribbed surfaces called “grooves” in the base of a carpet seaming iron. These function to form the thermoplastic adhesive of the carpet seam tape into beads just prior to being pressed into the carpet backing. These beads are thought to improve the penetration of the thermoplastic adhesive as it is pressed into the rough, porous carpet backing. This works to improve the strength of the seam. In addition to grooves, some of the carpet seaming irons disclosed in the above references include even deeper “center channels” in the base which form the adhesive into a heavier bead at the center of the seam where the two carpet edges are joined. The heavy center bead can function either to strengthen the seam along its centerline, or else can “butter” the edges of the carpet being seamed to seal the edges and prevent their unraveling.
These grooves and/or center channels create a problem in the manufacturing of carpet seam irons in that, within the valley area of these grooves or channels, there results an unusually thin cross-section in the base. The thin cross-sections present a problem in that it is desirable to mount certain temperature-sensing components of the carpet seaming iron directly to the base. Such components might include a bimetal thermostat, thermistor (in the case of electronic control), or over-temperature cutout. A prior art bimetal thermostat 10 including a typical fastener 11 used to fasten it to an iron base through a hole 12 is shown in FIG. 1. A prior art over-temperature cutoff 30 including two screws 31 used to fasten it to an iron base through holes 32 is shown in FIG. 2. Existing carpet seaming irons have used holes through the iron's base to mount bimetal thermostats and over-temperature cutoffs to the base, and other carpet seaming irons have mounted a thermistor to the iron base using a bracket with a screw and tapped hole.
But the use of conventional threaded fasteners and tapped holes to fasten components to the base of a carpet seaming iron can present problems. In the valley areas of grooves and channels, there is often insufficient material thickness remaining to form the necessary threads. The difficulty of tapping in such areas can result in unreliable production, a high scrap rate, and an unacceptably high number of field failures. What is needed is an improved means of fastening the necessary components to the base of the iron.
In addition, most prior art carpet seaming irons include a heat shield mounted within the assembly so that it is suspended above the base. This creates a gap between the heat shield and the base. This gap functions to reduce heat transfer between the heat shield and the base. It is preferred that the heat shield remain relatively cool (in comparison with the heating element) to protect the carpet as it passes over the heat shield. However, in order to further reduce heat transfer between the iron base and the heat shield, some irons include a gasket between the base and the heat shield. In irons including such a gasket, the gasket is normally placed on top of the iron's base. When the heat shield is fastened onto the iron, it then functions to hold the gasket down on the base.
However, providing a suitable gasket for the carpet seaming iron can be problematic because few available materials are certified to withstand the heat in this area of the carpet seaming iron (estimated up to 450 degrees). One common material is a high temperature silicone rubber, but such materials are soft, porous, and easily sliced apart when contacted by rough or sharp items such as knives that are commonly found in a tool box. What is needed is an improved means of forming a seal between the base of the iron and the heat shield.
Another unusual problem in the design of a carpet seaming iron is providing a convenient means of tending the power cord. Unlike clothes irons, in the use of a carpet seam iron, the user's focus is normally at the back of the device. This is the area where the carpet seam is put together and pressed into the molten thermoplastic adhesive. However, in the most popular carpet seam iron designs, the power cord comes out at the back of the handle and tends to get right in the way of the user's work. Hence, cord tenders have become a standard feature formed integrally as part of the handle of a carpet seaming iron specifically for the purpose of keeping the cord out of the user's way.
The most common type of prior art cord tender has a left indent, a center indent, and a right indent. A power cord can be positioned within either of the left indent or the right indent to position the cord to the right of the left, thus keeping it out of the working area at the back of the iron. The center indent is most often used to save space when the iron is put away and not in use.
Problems exist with this type of cord tender. First, the power cord must come with a strain relief over the cord jacket at the exit point from the handle. This strain relief must be flexible enough to permit positioning of the cord within the indents. However, it must also provide enough resistance to cord bending so that the cord is not easily bent into a tight radius that can damage the inner conductors.
The strain relief commonly disclosed in prior art carpet seaming irons is a “pigtail type” strain relief manufactured from steel wire and similar in appearance to a coil spring. Such pigtail-type strain reliefs terminate in a flared end to ensure a gradual bend radius at the exit of the strain relief when the cord is pulled or bent.
Problems also exist with the prior art cord tender when used in conjunction with a pigtail-type strain relief. Because the power cord and strain relief must be somewhat flexible, the power cord, even when positioned within an indent of the prior art cord tender, tends to droop under its own weight. Furthermore, as the iron is moved, the cord is pulled in the opposite direction due to being connected at the electrical receptacle at the wall. For these reasons, the cord can tend to move again towards the back of the iron, and into the way of the user's work.
To solve this problem, other prior art irons have used a “strain relief bracket,” which can support and extend the power cord further away from the iron handle to the left or right. One example works with a prior art cord tender and pigtail-type strain-relief. It consists of a tubular section with a jaw on one end and a distal end forming the exit location for the cord. The tubular section may have a longitudinal slot allowing it to fit over the body of the pigtail strain relief. Thus, to affix the bracket over the pigtail strain relief, the user slightly tugs on the flared end of the pigtail-type strain relief to lengthen it, and then fits the tubular section over the strain relief. When the flared end is released, the spring retracts against distal end of the device, holding it in position. The opposite jaw end of the device is designed to be positioned within the cord tender and hook itself within the valley formed by the left and right indents.
The strain relief bracket can be made from any semi-rigid material such as plastic, wood, or metal, and it may be formed as a single piece by molding. The device may not have the longitudinal slot, and is therefore meant to be permanently mounted to the assembly of the cord and strain relief, or the bracket may be mounted to the end of the iron handle using a ball joint and socket arrangement with the socket provided on the end of the handle and a ball joint extending from the end of the spacer arm. The spacer arm may be a top portion of a jaw area where strain relief bracket is hooked onto the cord tender portion of the iron handle. Relative to the handle, the spacer arm is a proximate end of the device. Such a bracket would conceivably be made from the same “semi-rigid” plastic, wood, or metal material.
One prior art iron uses a strain relief having a ball-shaped end that is formed through the joining of two end components. Both components may be made from a semi-rigid material, but on the “ball end” of the strain relief the iron also includes a round flanged shape. The two halves of the handle, when fastened together, internally form a pair of walls that retain this flange, while also permitting it to rotate. The iron thus includes a semi-rigid strain relief with an elongate tubular section that can rotate within its confines in the first handle half and second handle half. This achieves the object of extending the cord a distance away from the working area at the back of the iron.
But the strain relief bracket of this design has a problem in that the semi-rigid construction that provides the benefit of extending the cord also tends to defeat the function of the underlying strain relief. As the cord exits at a distal end 34, it is subject to the same stresses and wear that the underlying strain relief is supposed to reduce. Without a suitably flexible strain relief in such an area, the cord is likely to make a sharp bend whenever it is tugged off its axis, which can cause cord conductor damage. Because the strain relief of other devices are made from the same semi-rigid materials, they can have the same problems at the cord exit. Even if the designs include cutouts in the tubular extension area of their strain relief to make it more flexible, these cutouts are not as effective as they might be due to the use of semi-rigid material. Moreover, the semi-rigid material is brittle, causing the cutouts to crack over time and fail. Once the strain relief cracks, sharp bends of the cord become likely at the failure point.
Therefore, a strain relief is needed at the cord exit from any semi-rigid or rigid device component, such as a handle. The strain relief is preferably both flexible enough to form the cord into a gradual bend as it is tugged, while at the same time being resilient enough to prevent the cord from forming sharp bends. What is needed is an improved cord tender assembly for a carpet seaming iron that both tends the cord to the left or the right away from the working area at the back of the iron, while also providing effective strain relief in the attached power cord.